Jack-screw



(No Model.)

D. RANKIN.

- Jaok'Screw. No. 232,846. Patented Oct, 5,1880

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DAVID RANKIN, OF SAN FRANCISCO, CALIFORNIA.

JACK-SCREW.

SPECIFICATION formingpart of Letters Patent No. 232,846, dated October5, 1880.

Application filed June 30, 1880.

To all whom it may concern:

Be it knownthat I, DAVID RANKIN, a subject of the Queen of GreatBritain, and residing at San Francisco, in the county of San Franciscoand State of California, have invented a new and useful J ack-Screw, ofwhich the following is a specification.

My invention relates to improvements in jack-screws such as are used inthe lifting or moving of buildings and other heavy weights; and theobjects of my improvements are, first, to provide a jack-screw in whichthe cap which supports the weight is so constructed as to give a centraland not a side pressure to the capstan-head and screw-threaded shaftwhen being worked on an incline and while the screw-shaft is beingrevolved or worked; second, to provide a means whereby the screwthreadsof the shaft and base are relieved of th erincumbent weight or pressureafter the eight has been raised, and all danger of accidents which mightarise from the breakmg of the screw-threads is avoided; third, toprovide a device whereby the capstan-bar or handspike may be attached tothe body of the jack-screw in such manner as to form a handle by whichthe jack-screw may be carried from place to place; and, lastly, toprovide a means whereby the capstan-bar can be operated in a smallcompass or space.

I attain these objects by the mechanism illustrated inthe accompanyingdrawings, in which- Figure 1 is a side elevation; Fig. 2, verticalsectional elevation Fig. 3, top viewof cap.

Similar letters refer to similar parts throughout the several views.

The body or base A of my jack-screw I cast in the usual bell-shapedmold, and turn a screw-thread for a short distance in the upper partthereof.

The stem or shaft B of the capstan-head O is provided with a screwthread its entire length, and it engages with the screw-thread of thebody A.

The capstan-head G is pierced with two or a double series ofcapstan-holes, D D, the centers of the upper holes oropenings being overthe center of the web, between the lower (No model.)

it is impossible to make any but short turns of the capstan-head.

The top of the capstan-head is constructed in the form of a dome, asclearly seen in Fig. 2, and over this the cap or castle E fits, and isheld in position by a bolt or rivet, a. r

The cap or castle is hollowed out, as shown, so as to fit over the topof the capstan-head or dome, and the lower part of this cavity is ofgreater diameter than the upper part thereof, or of that portion of thecapstan-head upon which it rests and covers, the object being to permitthe cap to be slightly inclined when operating or working on an inclineor uneven ground. 1

Near the upper part of the base A, I secure the knob F, which has anaperture through which the handspike G is passed, and a step is formednear the bottom of the base A, in which the point of the handspikerests. A setscrew, 1), serves to secure the handspike in its position,as shown.

When in operation and the screw-shaft has been turned up a sufficientheight, and it is desirable that the superincumbent weight shall remainin a certain position for any length of time, I take the key or bar H,which, when not in use, hangs by a ring upon the knob F, and pass itthrough any two of a series of slots, I I, cut in the base A, and thenreverse the jack-screw a few turns, or until the lower end of thescrew-shaft rests upon the said key, and the pressure will then be takenoft the screwthreads and all danger of accident be avoided.

The part of the cap E which is applied to the weightto be operated uponis hollowed out, as shown, and the upper part or rim has a triangulargroove, 0, cut therein, so that it may take a firmer hold upon theweight to be lifted, and at the same time not scarify it as whenoperating with anotched cap.

Having thus described my invention, what I claim, and desire to secureby Letters Patent, is-

1. In a jack-screw, the combination of the capstan-head constructed in.the. form of a dome with the cap or castle hollowed out so as to bereceived by the said capstan-head in such a manner as to allow ofsufficient space for the easy working of the parts when united,substantially as herein set forth and described.

2. In a jack-screw, the combination, with the base A and cap E, of thescrew-threaded stem B and dome-shaped capstan-head 0, provided withrivet-bolt a and a series of holes,

and cap E, all arranged andoperating substantially as herein shown andset forth.* I 5 5. In a jackscrew, a carrying or lifting deviceconsisting of a knob or projection, F, setscrew 1), and capstan-bar Gr,substantially as set forth and described.

In testimony that I claim the foregoing I 20 have hereunto set my handand seal this 2d day of June, 1880.

DAVID RANKIN. n s.]

" Witnesses:

O. W. M. SMITH, W. P. COLEMAN.

